Progress towards Magnetic Memory at the atomic scale

A stable magnet made of a single atom – could this be a path to miniature magnetic storage devices? Maybe one day, thanks to the success of work done by Swiss, French, Serbian and Qatari scientists who have obtained a stable magnet in a single atom, and at a higher temperature than previous attempts.

The difficulty is to stabilise the magnetisation of such a small magnet. Researchers working at EPFL and ETHZ have just made such a magnet which is smaller and more stable until now, based on the rare earth element Holmium. The inconvenience: its working temperature is –233.15 °C – certainly low, but considerably better than previous records.

We know that magnets work due to the spin of the electron: a complex movement that can be represented by a spinning top. The electrons can orient themselves towards the top or the bottom, turning either clockwise or anti-clockwise, which creates a minute magnetic field. In an atom, electrons usually come in pairs, with opposite spins, hence mutually cancelling their magnetic fields. But in a magnet, the atoms have unpaired electrons, and their spin creates a magnetic field.

To allow their use in storage devices, researchers try to make smaller and smaller magnets. But they have the problem of magnetic remanence of such a magnet, very difficult to observe in a single atom.

By depositing single atoms of Holmium in ultra fine films of magnesium oxide with a surface of silver, the researchers have been able to form magnets of a single atom with a robust remanence.